This invention relates generally to couplers for optical fibers and more particularly to couplers for precisely aligning optical fibers in the vertical direction with other single-mode or multimode optical fibers or with optical components.
Optical communication has been seriously pursued especially since light-transmitting dielectric fibers or optical fibers were drastically improved in terms of propagation loss and mechanical strength. Optical fibers are usually made of various dielectric materials, such as silica or quartz, and have core diameters which range in size from a few microns to hundreds of microns.
One of the most important problems in optical communications is the connection or coupling between fibers, and also between fibers and various optical components. The coupling of the latter combinations is especially difficult due to geometric mismatch between fibers and other optical components. Coupling is more difficult in a single-mode fiber system than in a multimode fiber system because of the smaller core dimensions of single-mode fibers. For example, in the coupling between a single-mode fiber and a channel-waveguide, a mismatch of one micron may reduce coupling efficiency by as much as 50 percent. Conventional techniques for precise optical coupling are expensive; have one or more grooves in only one direction and include cumbersome means, such as a plurality of screws, for aligning optical fibers so that coupling to within micron tolerances is impractical; and in some devices, only one fiber may be aligned at a time.